3-(trihydrocarbylphosphoranylidene)-2,5-pyrrolidinediones as latent catalysts for promoting the reaction between phenols and epoxy resins

ABSTRACT

The 3-(trihydrocarbylphosphoranylidene)-2,5-pyrrolidinediones are novel latent catalysts for promoting the reaction between epoxides and phenols. Examples of said catalysts include   WHEREIN R is phenyl or n-butyl.

States Patent 1191 Schmidt et al.

[ 1 Oct. 22, 1974 i 1 S-(TRIIIYDROCA RBYLPI-IOSPHORANYLIDENE)-2,5- PYRROLIDINEDIONES AS LATENT CATALYSTS FOR PROMOTING THE REACTION BETWEEN PI-IENOLS AND EPOXY RESINS {75] Inventors: Dennis L. Schmidt, Lake Jackson,

Tex.; George A. Doorakian,

Waltham, Mass.

[73] Assignee: The Dow Chemical Company,

Midland, Mich.

[22] Filed: Nov. 28, 1973 [21] Appl. No.: 419,737

Related US. Application Data [63] Continuation-impart of Ser. No. 290,889, Sept. 21,

I972. abandoned.

[56] References Cited UNITED STATES PATENTS 3,356,645 12/1967 Warren 260/47 Primary ExaminerWilliam l-l. Short Assistant Examiner-T. Pertilla Attorney, Agent, or Firm-L. Wayne White 5 7 ABSTRACT The 3-(trihydrocarbylphosphoranylidene)-2,5- pyrrolidinediones are novel latent catalysts for promoting the reaction between epoxides and phenols. Examples of said catalysts include wherein R is phenyl or n-butyh I 14 Claims, N0 Drawings 3-(TRIHYDROCA RBYLPHOSPHORANYLIDENE)-2,5- PYRROLIDINEDIONES AS LATENT CATALYSTS FOR PROMOTING THE REACTION BETWEEN PHENOLS AND EPOXY RESINS CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of our copending application Ser. No. 290,889, filed Sept. 21, l972 and now abandoned.

BACKGROUND OF THE INVENTION l. Field of the Invention This invention pertains to novel latent catalysts for promoting the reaction between epoxides and phenols. The invention pertains particularly to novel latent catalysts for promoting the reaction between polyhydric aromatic compounds (phenols) and epoxy resins (polyepoxides).

2. Description of the Prior Art The class of compounds here referred to as epoxy resins" is well known and includes many members. Epoxy resins bear an average of more than one oxirane (epoxy) group per molecule. They react with a variety of compounds bearing active hydrogen, e.g., phenols, primary and secondary amines, mercaptans, water, etc., to form the corresponding phenolic ether, secondary or tertiary amine, thioether, etc.

The reaction of epoxy resins with appropriate phenols is a convenient method of increasing the molecular weight of the epoxy resin but otherwise retaining their basic chemical characteristics.

The reaction of epoxy resins with phenolic hydroxyl groups is rather slow but is promoted (catalyzed) by bases and quaternary ammonium compounds. Several problems are normally encountered when using such catalysts. For example: First, they usually react with the epoxy resin alone and thus preclude the option of marketing what is known in the art as a precatalyzed epoxy resin. Second, they are typically nonselective in that they promote the reaction of epoxy resin with both the phenolic hydroxyl groups of the reactant and the aliphatic hydroxyl groups in the product. This results in undesirable branching and/or cross-linking. Third, they generally have to be blended with the epoxy resin and phenolic reactants just prior to use because of the high rate of subsequent reaction. Proper formulation and complete mixing under such circumstances are difficult.

These and other problems have now been solved by the subject invention.

SUMMARY OF THE INVENTION the 3- Additionally, the subject catalysts are specific in that they promote the reaction of epoxy resins with phenolic hydroxyl groups to a far greater extend than they extent the reaction of epoxy resin with aliphatic hydroxyl groups in the reaction product. Thus, little if any branched and/0r cross-linked product is formed by reacting a difunctional epoxy resin with a difunctional phenol in the presence of the subject catalysts.

Finally, the subject catalysts are unique because their catalytic activity is latent at temperatures below about 50C. Consequently, mixtures of epoxy resins, phenols and the subject catalysts have greatly extended pot lives over prior art mixtures. In those instances where the epoxy resin is essentially unreactive toward the phenol (absent a catalyst or elevated temperature), the subject catalysts can be added and the mixtures marketed as a completely formulated composition.

The Catalysts The 3-(trihydrocarbylphosphoranylidene)-2,5- pyrrolidinediones are, as a class, generally known. Each member of the class has the basic nucleus:

wherein R, is hydrogen or hydrocarbyl andis preferably hydrigen, R -R are hydrocarbyl, and R is hydrogen or hydrocarbyl. Such compounds are conventionally prepared by contacting a trihydrocarbylphosphine with maleimide or an inertly substituted derivative thereof. Such compounds therefore include 3-trialkyl-,

3-triaryl-, 3-trialkaryl 3-triaralkyl ,TtricycIoalky I and 3-(trialkenylphosphoranylidene) 2,5- pyrrolidinediones and the like. Illustrative examples include: 3-trimethyl-, 3-triethyl-, 3-tri(n-butyl)-, 3- trihexyl-, 3-tridecyl-, 3-tridodecyl-, 3-trioctadecyl-, 3-di(n-butyl)-3-hexyl-, 3-triphenyl-, 3-tri(methylphenyl)-, 3-tri(butylphenyl)-, 3-tri(octylphenyl)-, 3- tri(benzyl)-, 3-tri(phenethyl), 3-tri('phenylbutyl)-, 3-tri(3,5-dimethylbenzyl)-, 3-tricyclohexyl-, 3-triallyl-, 3-cyclohexenylphosphoranylidene-2,5- pyrrolidinedione and the corresponding compounds bearing a hydrocarbyl substituent in'the 4-position such as 4-methyl, 4-ethyl, 4-propyl, 4-butyl, 4-phenyl, etc., and other like compounds, and the corresponding compounds bearing an N-hydrocarbyl substituent, such as l-methyl, l-ethyl, l'hexyl, l-decyl, l-octadecyl, lphenyl, l-naphthyl, l-tolyl-, l-allyl, l-benzyl, lcyclohexyl, etc. Mixtures of such compounds can also be used.

The amount of catalyst used can be varied overa wide range. Generally, however, they are used in concentrations of from about 0.001 to about 10 percent by weight, based on the combined weight of epoxy resin The Reactants As stated above, the reactants here used are wellknown classes of compounds. This is illustrated, for example, by USP Pat. Nos. 2,216,099, 2,633,458, 2,658,885, 3,477,990 and the text Handbook of Epoxy Resins by Lee and Neville. McGraw-Hill (NY. l967 Each member of these known classes is suitable for use herein.

The Epoxy Reactants The vicinal epoxides, for example, are organic compounds bearing one or more groups. The alkylene oxides of from 2 to about 24 carbon atoms, the epihalohydrins and the epoxy resins are perhaps the best known and most widely used members of the genus. Ethylene oxide, 1,2-propylene oxide, 1,2- butylene oxide and epichlorohydrin are the preferred monoepoxides. There are two preferred subclasses of epoxy resins. The first subclass corresponds to the general formula wherein R is hydrogen or an alkyl radical of 1-4 carbon atoms (and is preferably hydrogen) and n is from about 0.1 to about 10, preferably from about 1 to about 2. Preparation of these polyepoxides is illustrated in US. Pat. Nos. 2,216,099 and 2,658,885. The second subclass corresponds to the general formula monohydric phenols as well as polyhydric phenols, such as resorcinol, hydroquinone, etc. The polyhydric phenols bearing from 2 to 6 hydroxyl groups and having from 6 to about carbon atoms are particularly useful in the reaction with epoxy resins to form high molecular weight resins (linear or cross-linked) useful in coatings. Particularly preferred polyhydric phenols are those corresponding to the formula wherein R" is hydrogen, halogen (fluoro, chloro or bromo) or hydrocarbyl and X is oxygen, sulfur, SO-, SO bivalent hydrocarbon radicals containing up to 10 carbon atoms, and oxygen, sulfur and nitrogemcontaining hydrocarbon radicals, such as wherein R, R',, R' and R' are each independently hydrogen, bromine and chlorine and wherein A is an alkylene (e.g., methylene) or alkylidene (e.g., isopropylidene) group having from about I to about 4 carbon atoms, or A is The diglycidyl ether of 4,4'-isopropylidenediphenol is the most preferred epoxy resin.

The Phenolic Reactants The phenols are organic compounds having one or more hydroxyl groups attached to an aromatic nucleus. This class of compounds therefore includes phenol, alpha and beta-naphthol, o-, m-, or p-chlorophenol, alkylated derivatives of phenol (e.g., o-methyl-, 3,5- dimethyl-, p-t-butyland p-nonylphenol) and other and -SO-l-R"SO2 radicals wherein R is a bivalent hydrocarbon radical. 4,4Isopropylidenediphenol (i.e., bisphenol A) is the most preferred phenol.

Ratio of Reactants The ratio of epoxide to phenol in the subject process can vary over a wide range depending upon the product desired. H.g. if a product terminated with a phenolic ether group is desired, obviously one would employ an excess of phenol in the process, etc.

Solvents Other Process Parameters Generally, the reaction mixture is warmed at temperatures in the range of from about 50C. to about 225C. (preferably lOO-l75C.) until an exotherm begins and, after the exotherm has peaked, subsequently warmed in the same range for an additional time to assure substantially complete reaction. Atmospheric or superatmospheric pressures (e.g., up to about 200 psig.) are common.

The Reaction Products The products here produced are generally known compounds in industry. The particular product produced will vary in properties depending upon the selection and ratio of reactants used in the process. Every combination of reactants, of course, need not be discussed but the following discussion will illustrate the types of products which can be produced.

The reaction products here produced by reacting an epoxy resin with a phenol in the presence of the subject catalysts are phenolic ethers bearing one or more aliphatic secondary hydroxyl groups. Such aliphatic hydroxyl groups are formed in the ring-opening reaction between the oxirane and phenolic hydroxyl groups. Additionally, the reaction products bear a terminal epoxy group(s) or a phenolic hydroxyl group(s) depending upon the ratio of reactants. Consequently, they are reactive intermediates which can be cured (cross-linked) with many polyfunctional curing agents to form hard, insoluble solids which are useful coatings. A listing of several known curing agents which are suitable for use herein is found in U.S. Pat. No. 3,477,990. The cured products (particularly those of high molecular weight) are useful as surface coatings, as adhesive layers in laminates, coatings on filament windings, in structural binding applications, and the like. The reaction products prepared from halogenated (particularly brominated) phenols are particularly useful in flameproofingapplications since they tend to be self-extinguishing. Thus, they are useful in forming cured coatings for wood paneling and as adhesive layers in wood laminates, etc.

Hydraulic fluids are here prepared by reacting a lower alkylene oxide with a phenol in substantially equimolar amounts. E.g., C H OCH CH OH and C H4O(CH CH O) I-I are illustrative.

Experimental The following examples further illustrate the invention.

Example 1 To a reaction vessel equipped with a stirring means and a temperature recording means were charged under a nitrogen purge 75.79 parts by weight of the diglycidyl ether of 4,4-isopropylidenediphenol, 24.21 parts of 4,4'-isopropylidenediphenol (bisphenol A) and 0.15 part of 3-(triphenylphosphoranylidene)-2,5- pyrrolidenedione dissolved in about 5 ml. of methanol. The stirred reaction mixture was warmed from ambient temperature to 150C. at a rate of 3C./minute. At 150C the heat was turned off. A reaction exotherm occurred which peaked at about 213C. The reaction mixture was warmed at 150C. for an additional 2.5 hours after the exotherm subsided. Theoretical epoxide content 8.20 percent. Observed 8.13 percent.

Examples 2-3 In like manner 377.5 g. of the diglycidyl ether of bisphenol A reacted with 122.5 g. of bisphenol A in the presence of: (2) 1-methyl-3- (triphenylphosphoranylidene )-2,5-pyrrolidinedione (0.573 g.), (3) 1-phenyl-3- (triphenylphosphoranylidene)-2,5-pyrrolidinedione (0.68 g.). The reaction mixture in each instance was warmed to C. at a rate of about 5C./minute, the temperature allowed to exotherm, and each mixture subsequently warmed for 5 hours at C. Theoretical epoxide content for Examples 2 and 3 is 8 percent. Observed 7.81 percent and 7.82 percent for Examples 2 and 3, respectively.

Examples 4-6 The procedure of Example 2 was followed except that different catalysts were used and the finishingheating step was 2 hours at 160C. instead of 5 hours. The catalysts here used were (4) l-phenyl-3-(tri-nbutylphosphoranylidene)-2,5-pyrrolidinedione (0.45 8 g.), (5) 3-(diethyl phenyl phosphoranylidene)-2,5- pyrrolidinedione (0.408 g.) or (6) 3-(diphenyl ethyl phosphoranylidene)-2,5-pyrrolidinedione (0.478 g.). Theoretical epoxide content for Examples 4-6 is 8 percent. Observed 7.82 percent, 7.84 percent and 7.92 percent for Examples 4-6, respectively.

Precatalyzed epoxy resins were prepared by blending the diglycidyl ether of bisphenolA (EEW 187) with the catalysts named in Examples 1-6. These mixtures were stored for up to four weeks at 50 C. and used inexperiments otherwise identical to Examples l-6. The stored mixtures showed little, if any, loss in reactivity and their reaction products with phenols hadessentially the same properties as those obtained in Examples l-6.

The products produced in Examples 1-6 were substantially linear compounds. They are curable (crosslinkable) with conventional curing agents, such as dicyanamide, polyamines, anhydrides, etc. The cured resins are tough solvent resistant materials which are useful as coatings.

Branched and/or cross-linked products are similarly prepared in the instant process by (l) reacting 'an epoxy resin having at least 3 epoxy groups per molecule with a phenol having at least 2 hydroxyl groups, or (2) by reacting an epoxy resin having at least 2 epoxy groups per molecule with a phenol having at least 3 hydroxyl groups in the presence of the subject catalysts. Such branched and/or cross-linked products are likewise useful as coatings.

We claim: 1 v

l. A precatalyzed epoxy resin composition comprising (a) an epoxy resin bearing an average of more than one vicinal epoxy group per molecule and (b) a small but catalytic amount of a 3 (trihydrocarbylphosphoranylidene)-2,5- pyrrolidinedione.

4. The composition defined by claim 1 wherein (b).-

is a l-hydrogen-3-(trialkyl or triarylphosphoranylidene)-2,5-pyrrolidinedione.

5. The composition defined by claim 1 wherein (a) corresponds to the formula j V, 11 Hrs. s? L J i wherein R is hydrogen or an alkyl radical of 1-4 carbon atoms and n varies from 0.1 to about 10.

6. The composition defined by claim 1 wherein (a) 10 corresponds to the formula wherein R, R R' and R';, are hydrogen, chloro or bromo;

and A is an alkylene or alkylidene group of from 1 to 4 carbon atoms or A is 7. The composition defined in claim 6 wherein (a) is the diglycidyl ether of 4,4'-isopropylidenediphenol and (b) is l-(hydrogen, methyl or phenyl)-3-(triphenylphosphoranylidene)-2,5-pyrrolidinedione or l-phenyl- 3-(tri-n-butylphosphoranylidene)-2,5-pyrrolidinedione or 3-(diphenylethylor diethylphenylphosphoranylidene)-2,5-pyrrolidinedione.

8. A composition comprising (a) an epoxy resin bearing an average of more than one epoxy group per molecule. (b) a polyhydric phenol and (c) a small but sufficient amount of a 3- (trihydrocarbylphosphoranylidene)-2.5- pyrrolidinedione to catalyze the reaction of (a) with (b) when warmed at a temperature of from about 50C. to about 225C. 55

9. The composition defined by claim 8 wherein (b) is polyhydric phenol of from 6 to about 30 carbon atoms bearing from 2 to 6 hydroxyl groups.

l0. The composition defined by claim 9 wherein (b) is a polyhydric phenol corresponding to the formula 11. The composition defined by claim 1 0 wherein (b) is 4,4-isopropylidenediphenol.

12. The composition defined by claim 9 wherein (a) is an epoxy resin corresponding to the formulae (!)CHz-CH-CHz R O-CHzCH--CH2 wherein R is hydrogen or an alkyl radical of 14 carbon atoms and n is from about 0.1 to about 10, or

wherein R, R',, R' and R';, are hydrogen, bromine or chlorine, and A is S, SS-, S(O), SO C(O), --O, alkylene of l to 4 carbon atoms or alkylidene of l to 4 carbon atoms, and wherein (c) is present in an amount of from about 0.001 to about 10 percent by weight, based on the combined weight of (a) and (b).

13. The composition defined by claim 12 wherein (a) is the diglycidyl ether of 4,4'-isopropylidenediphenol, (b) is 1-( hydrogen, methyl or phenyl)-3- (triphenylphosphoranylidene)-2,5-pyrrolidinedione or l-phenyl-3-( tri-nbutylphosphoranylidene 2,5- pyrrolidinedione or 3-(diphenylethylor diethylphenylphosphoranylidene)-2,5-pyrrolildinedione and (c) is 4,4isopropylidenediphenol, and wherein (b) is present in an amount of from about 0.05 to about 5 percent by weight, based on the combined weight of (a) and (b).

14. In the process of reacting by contacting a vicinal epoxide with a phenol, the improvement consisting of conducting said process at a temperature of from about 50C. to about 225C. in the presence of a small but catalytic amount of a 3- (trihydrocarbylphosphoranylidene)-2,5- pyrrolidenedione. 

1. A PRECATALYZED EPOXY RESIN COMPOSITION COMPRISING (A) AN EPOXY RESIN BEARING AN AVERAGE OF MORE THAN ONE VICINAL EPOXY GROUP PER MOLECULE AND (B) A SMALL BY CATALYTIC AMOUNT OF A 3-(TRIHYDROCARBYLPHOSPHORANYLIDENE)-2,5PYRROLIDINEDIONE.
 2. The composition defined by claim 1 wherein (b) is a 1-hydrocarbyl-3-(trihydrocarbylphosphoranylidene)-2,5-pyrrolidinedione.
 3. The composition defined by claim 2 wherein (b) is a 1-(alkyl or phenyl)-3-(trialkyl- or triaryl-phosphoranylidene)-2,5-pyrrolidinedione.
 4. The composition defined by claim 1 wherein (b) is a 1-hydrogen-3-(trialkyl or triarylphosphoranylidene)-2,5-pyrrolidinedione.
 5. The composition defined by claim 1 wherein (a) corresponds to the formula
 6. The composition defined by claim 1 wherein (a) corresponds to the formula
 7. The composition defined in claim 6 wherein (a) is the diglycidyl ether of 4,4''-isopropylidenediphenol and (b) is 1-(hydrogen, methyl or phenyl)-3-(triphenyl-phosphoranylidene)-2,5-pyrrolidinedione or 1-phenyl-3-(tri-n-butylphosphoranylidene)-2, 5-pyrrolidinedione or 3-(diphenylethyl- or diethylphenylphosphoranylidene)-2,5-pyrrolidinedione.
 8. A composition comprising (a) an epoxy resin bearing an average of more than one epoxy group per molecule, (b) a polyhydric phenol and (c) a small but sufficient amount of a 3-(trihydrocarbylphosphoranylidene)-2,5-pyrrolidinedione to catalyze the reaction of (a) with (b) when warmed at a temperature of from about 50*C. to about 225*C.
 9. The composition defined by claim 8 wherein (b) is polyhydric phenol of from 6 to about 30 carbon atoms bearing from 2 to 6 hydroxyl groups.
 10. The composition defined by claim 9 wherein (b) is a polyhydric phenol corresponding to the formula
 11. The composition defined by claim 10 wherein (b) is 4,4''-isopropylidenediphenol.
 12. The composition defined by claim 9 wherein (a) is an epoxy resin corresponding to the formulae
 13. The composition defined by claim 12 wherein (a) is the diglycidyl ether of 4,4''-isopropylidenediphenol, (b) is 1-(hydrogen, methyl or phenyl)-3-(triphenylphosphoranylidene)-2,5-pyrrolidinedione or 1-phenyl-3-(tri-n-butylphosphoranylidene)-2, 5-pyrrolidinedione or 3-(diphenylethyl- or diethylphenylphosphoranylidene)-2,5-pyrrolildinedione and (c) is 4,4''-isopropylidenediphenol, and wherein (b) is present in an amount of from about 0.05 to about 5 percent by weight, based on the combined weight of (a) and (b).
 14. In the process of reacting by contacting a vicinal epoxide with a phenol, the improvement consisting of conducting said process at a temperature of from about 50*C. to about 225*C. in the presence of a small but catalytic amount of a 3-(trihydrocarbylphosphoranylidene)-2,5-pyrrolidenedione. 